Driving and stopping mechanisms utilizing pumps of the variable output type



Sept. 3, 1968 B. w. GREENE ET AL 3,399,641

DRIVING AND STOPPING MECHANISMS UTILIZING PUMPS OF THE VARIABLE OUTPUT TYPE Filed Feb. 26, 1965 United States Patent DRIVING AND STOPPING MECHANISMS UTI- LIZING PUMPS OF THE VARIABLE OUTPUT TYPE Blandford W. Greene, Manchester, and Robert J. Desmond, Ipswich, Mass., assignors to United Shoe Machinery Corporation, Flemington, N.J., a corporation of New Jersey Filed Feb. 26, 1965, Ser. No. 435,597 5 Claims. (Cl. 112-219) ABSTRACT OF THE DISCLOSURE A driving and stopping mechanism for a machine such as a heavily constructed shoe sewing machine including a shaft, a displacement unit connected to the shaft and driven by a variable output pump, a treadle to control the output of the pump and a differential :pressure relief valve arranged to retard the rotation of the shaft below that corresponding to the output of the pump.

This invention relates to improvements in hydraulic driving and stopping systems for a heavy sewing machine of the type disclosed in United States Letters Patent No. 3,142,278, granted July 28, 1964, upon application of Copithorne et al., which driving and stopping systems are provided with a positive stop dog arranged to be engaged by a shoulder on a part rotating with a main operating shaft for an operation performing machine.

In the driving and stopping mechanisms of the prior patent two separate pumps and a single hydraulic displacement unit, together with suitable control valves, are required, one pump being employed to drive the displacement unit at low speed, and another pump to drive the displacement unit at variable higher speeds depending upon the position of an operator-controlled treadle. While the system disclosed in that patent is extremely effective and easily controlled by the operator, it is complicated and expensive to manufacture, so that it is highly desirable to simplify and improve the construction of the system without detracting from its effectiveness and ease of control. It is accordingly an object of the present invention to provide simplified hydraulic driving and stopping mechanisms for use with a heavily constructed sewing machine of the type referred to in the prior patent, which mechanisms will be more economical to manufacture and more easily serviced and maintained without sacrificing any of the desirable features of the prior driving and stopping mechanisms.

As hereinafter disclosed, the present driving and stopping mechanisms include a main shaft for actuating a driven machine, a displacement unit mechanically connected to the main shaft, a positive stop mounted for movement toward and from an active position to bring the main shaft to rest in a predetermined position through impact by a member rotating with the main shaft, in which a single :pump of the variable output type is hydraulically connected to the displacement unit, and a yieldingly actuated treadle is arranged to increase or decrease the output of the pump, wherein means are provided for limiting the yielding movement of the treadle to correspondingly reduce the shaft speed to a value below that which will produce a destructive shock or jar on the positive stop when it is impacted by the rotating member. To insure that there is no possibility of creating a vacuum and resultant hydraulic shock between the pump and the displacement unit, a differential pressure relief valve having two remote control tubes is arranged with one tube connected to an inlet conduit running to the displacement unit and the other connected to an outlet conduit run- 3,399,641 Patented Sept. 3, 1968 ning from the displacement unit. By so arranging the relief valve, the shaft speed may be reduced by direct pumping action of the displacement unit below that corresponding to the output of the pump, thus preventing any undesirable suction in the outlet conduit.

The use of a variable outlet pump and a differential control valve are particularly advantageous with a sewing machine which requires stopping precisely in a predetermined position. 7

These and other features of the invention, as hereinafter described and claimed, will be apparent to those skilled in the art from the following detailed specification taken in connection with the accompanying drawings, in which FIG. 1 is a fragmentary perspective view looking from the right front of a heavily constructed shoe outsole sewing machine, together with a diagrammatic illustration of hydraulic and electrical control systems employed in operating the machine, according to the present invention and in bringing the machine to rest Within a single rotation of its main sewing shaft;

FIG. 2 is a detail view, partly broken away, to reduce over-all dimensions and to illustrate internal construction of a treadle-controlled variable displacement pump employed in the system illustrated in FIG. 1; and

FIG. 3 is a sectional detail view of a differential pressure relief valve employed in the system.

The driving and stopping mechanism disclosed herein is arranged to impart rotation to a main operating shaft of a heavily constructed sewing machine having stitch forming devices 8, similar to those identified in the prior patent above referred to. The sewing shaft is brought to a predetermined rest position after operating at variable speed under the control of the operator, the shaft being driven at slow speed through a fraction of a turn precisely to its rest position where the slow speed drive is terminated and the shaft is permitted to stop without imparting excessive shock or jar to the heavy machine parts. To locate accurately its position of rest, the main shaft is provided with a positive mechanical stop against which is engaged a shoulder on a cam secured to the sewing shaft. The positive stop comprises a stopping dog pivoted on a fixed shaft in the machine and normally held out of the path of the cam by the control treadle during sewing operations.

The sewing shaft for actuating the stitch forming devices of the illustrated machine is indicated at 10, to which shaft is mechanically coupled a hydraulic diplacement unit 12 arranged not only to drive the shaft but adequately to 'dissipate the energy required to regulate the speed effectively and to bring the shaft to a sufiiciently reduced speed of rotation that impact of the shoulder on the cam, indicated at 14 on the stopping dog, indicated at 16, will not impart to it a destructive shock or jar. The stopping dog 16 is in the form of an arm pivotally mounted for movement in two directions, one parallel to the length of the shaft 10 and the other transversely of the shaft. While engaging the cam 14 the dog is moved radially of the shaft to perform auxiliary operations in the sewing machine, such as releasing the work from the machine and reducing the tension on the sewing thread, so that the work operated upon may readily be removed from the machine.

The stopping dog 16 at its upper cam engaging end is provided with a roll 18 against which the shoulder on the cam acts and the lower end of the stopping dog is pivoted on a pair of dia-metric screws, one of which is illustrated at 20, engaging recesses in a sleeve 22 rotatable on a fixed shaft 24.

To assist the hydraulic displacement unit in dissipating stopping energy, as disclosed in the prior patent, an outlet conduit running from the displacement unit is connected with a flow restricting circuit provided with a small orifice.

The driving and stopping mechanism of the present invention avoids the necessity of utilizing a flow restricting circuit to dissipate the stopping energy of the machine, a differential pressure relief valve 26 being connected to the outlet conduit 28 of the displacement unit in such manner that the relief valve is opened automatically whenever pressure is exerted in an inlet conduit 30 of the displacement unit, as might occur when the hydraulic displacement unit is being driven during normal driving conditions. When the relief valve 26 is closed a positive pressure quickly builds up in the outlet conduit to stop the displacement unit. With such an arrangement it is possible to utilize a variable output type of hydraulic pump 32 controlled by a yieldingly actuated treadle 34, movement of the treadle being limited in its yielding movement to correspondingly reduce the volume of fiuid passing through the pump to a value below that which will produce a destructive shock to the positive stop before it is engaged by the cam 14 rotating with the sewing shaft.

As illustrated, the variable output pump is of the piston type identified as PVBlS obtainable from Vickers, Inc., 14420 Linwood Ave., Detroit, Mich, and is provided with a control lever 36 movable to either side of a neutral or non-pumping position. As illustrated, operation of the control lever is movable to one side only of its neutral position, so that fluid flow is always in one direction. For so limiting the movement of the control lever, an adjustable stop in the form of a screw 38 is threaded into a bracket 40 secure-d to a housing 42 for the pump 32. The control lever 36 is clamped to one of two pins 44 rotatable in a housing 42 for the pump and is secured inside the pump to a yoke '46 which provides a guide for imparting movement to a series of pistons reciprocating in a cylinder block, the length of stroke imparted to each piston being variable with changes in the angular position of the yoke.

The position of the stop screw 38 is adjusted to prevent movement of the yoke into its neutral position, so that when the operator removes his foot from the treadle 34 a spring 48 for yieldingly actuating the treadle into its raised position shifts the yoke into an angularity which will produce a fluid flow through the displacement unit 12 to produce rotation of approximately 120 rpm. in the main sewing shaft of the machine. This speed of rotation is safely below that which would produce destructive shock or jar on the stopping dog 16 as it is engaged by the shoulder on the rotating cam 14. Releasing the treadle 32, therefore, tends to reduce the speed of the displacement unit to a safe non-shock producing rate, the stopping dog 16, after moving into the path of the cam 14 acting to bring the sewing shaft of the machine to rest at a predetermined fixed position within a single rotation of the shaft.

It is readily apparent that when the sewing shaft is rotating at maximum speed and the treadle 32 is released the pressure of the hydraulic fluid in the inlet conduit 30 of the displacement unit is reduced substantially, depending upon how quickly the treadle is released. The pressure may be reduced below that of the atmosphere so that a vacuum exists. Reduction in pressure in the inlet conduit 30 causes a corresponding drop of pressure in low pressure control tube 48 communicating with a space beneath a piston 50 in the differential valve 26, the whole area of the piston being acted upon by the pressure in the tube 48. To resist the movement of the piston 50 by pressure its upper end has an enlarged valve portion 52 between which and an adjusting screw 54 is confined a spring 56. Normally the adjusting screw is regulated to cause the valve 52 to open a port 58 in the valve body whenever the pressure in the tube 48 exceeds 125 lbs. per square inch, this value of pressure being sufiicient to produce rotation of the sewing shaft 10 by the displacement unit 12 at a speed corresponding to the output of the pump 32.

To protect the valve and the displacement unit from damage by excessive pressures in the outlet conduit 28 through which the fluid flows when the valve 52 moves downwardly to close the port 58 a second pilot tube 60 enters the lower portion of the casing for the valve 26 to exert its pressure on the lower end of a small diameter piston 62 engaged with the lower surface of the piston 50, the area of the piston 62 being one-eighth of that for the piston 50. Thus the force required to lift the valve 52 by pressure within the pilot tube 60 is 1,000 lbs. per square inch. Since the pilot tube 60 is connected to the outlet conduit 28 a strong braking force will be applied to resist rotation of the displacement unit 12 whenever the pressure within the pilot tube 48 in reduced below 125 lbs. In this way an extremely reliable and quick acting speed reduction is obtainable whenever the treadle 34 is released.

If the displacement unit should actually bring the sew ing sha'ft momentarily to rest on account of closure of the relief valve 26 it would immediately startrotating again at low speed since the setscrew 38 of the pump is adjusted to produce a small flow of fluid. To reduce the possibility that the hydraulic fluid will be drained from the displacement unit when the capacity of the pump is reduced momentarily below that of the displacement unit, the inlet conduit 30 has interposed in it a check valve 64.

The pump 32 receives its supply of fluid through a suction tube 66 at the lower end of which is a strainer 68 immersed in a sump 70. As an over-all safety device the inlet conduit 30 running from the pump to the displacement unit is connected to a tube 72 extending to a combination pressure relief and pilot valve 74. The outlet from the valve 74 is connected to a drain 76 extending also to the differential relief valve 26. For venting all of the fluid from the relief valves 26 and 74, the drain 76 has connected with it a filter 78 and a return tube 80 extending to the sump 70.

As disclosed in an application for United States Letters Patent Ser. No. 377,618, filed June 24, 1964, now U.S. Patent No. 3,291,083, the present driving and stopping mechanisms are provided with a pressure release control, so arranged that when the machine is brought to rest the variable output pump 32 may be driven idly by a suitable driving motor, indicated at 82, Without consumption of unnecessary power. To this end, the Sewing shaft 10 has secured to it in closely spaced relation to the cam 14 a second cam 83 arranged to be engaged by a follower lever 84 connected in parallel relation to the stopping dog 16 and movable with the dog axially of the shaft 10 but independently in a direction radially of the sewing shaft, the stopping dog 16 and the lever 84 being connected by a screw and slot connection 86, so that the two are free to move radially in different directions. The follower lever 84 is yieldingly urged into and out of the path of the cam 83 and moves with the stopping dog similarly with relation to its respective cam. The follower lever 84 is pivotally mounted for movement with the stopping dog on a pair of radial pins, one of which is shown at 88 carried by a hub of an arm 90 rotatably mounted on the shaft 24, which also supports an auxiliary operation performing lever 92 extending from the sleeve 22. At the rearward end of the lever 90 there is an adjusting screw 94 arranged to engage a movable switch arm 96 to separate a movable contact on the arm from a stationary contact 98 to open an electrical circuit 99 to an actuating solenoid for a control valve 100. The control valve 100, when actuated by its solenoid, blocks a bleed line 102 running from the pilot valve 74, thus causing the valve to relieve pressure in the tube 72 and permit the fluid therein to drain into the sump 70. Thereafter, no load is imposed on the motor 82 during continued operation of the motor, the pump 32 causing the fluid in the tube 72 to flow freely into and out of the sump.

The nature and scope of the invention having been indicated and a particular embodiment having been disclosed, what is claimed is:

1. Hydraulic driving and stopping mechanisms for rotating a shaft, including a member rotating with the shaft, a positive stop mounted for movement toward and from an active position to bring the shaft to rest in a predetermined angular position through impact by the rotating member, a displacement unit mechanically connected to the shaft, a pump of the variable output type having an inlet conduit and an outlet conduit, a pressure conduit hydraulically connected between the displacement unit and the pump, in combination with a yieldingly actuated treadle-coupled to the positive stop and connected to the pump to increase or decrease its output, and means for limiting the yielding movement of the treadle to correspondingly reduce the main shaft speed to a value below that which will impart a destructive shock to the positive stop when it is impacted by the rotating member.

2. Hydraulic driving and stopping mechanisms for rotating a shaft, including a member rotating with the shaft, a positive stop mounted for movement forward and from an active position to bring the shaft to rest in a predetermined angular position through impact by the rotating member, a displacement unit mechanically connected to the shaft, a pump of the variable output type having an inlet conduit and an outlet conduit, a pressure conduit hydraulically connected between the displacement unit and the pump, in combination with a yieldingly actuated treadle coupled to the positive stop and connected to the pump to increase or decrease the output of the pump and a differential pressure relief valve having two remote control tubes, one connected to the outlet conduit and the other connected to the inlet conduit to retard rotation of the shaft below that corresponding to the output of the pump.

3. A machine for performing an operation, as in claim 2, in which the remote control tube connected to the outlet conduit requires a higher pressure to open the relief valve than the control tube connected to the inlet conduit.

4. A sewing machine having stitch forming devices, a main sewing shaft for actuating the stitch forming devices, means for driving the sewing shaft under variable control by an operator of the machine including a hydraulic displacement unit mechanically connected to the sewing shaft, a stop cam on the sewing sha'ft having a radial shoulder and a pivotally mounted dog arranged to move into and out of the path of said cam and to be engaged by the radial shoulder when the shaft reaches a predetermined stopping position in combination with a variable output pump and a differential pressure relief valve hydraulically connected to the displacement unit, the differential pressure relief valve having two remote control tubes, one connected to an inlet conduit running to the displacement unit and the other connected to an outlet conduit running to the displacement unit to apply a back pressure to the displacement unit and to reduce the main shaft speed to a value below that which will impart a destructive shock to the positive stop.

5. A sewing machine according to claim 4 further comprising a check valve in the inlet conduit running to the displacement unit to prevent pressure from the displacement unit from interfering with the control of the relief valve.

References Cited 

